A Sanford police officer charged with petty theft after a police ''sting'' operation was found not guilty Thursday after a daylong retrial.

After deliberating for only six minutes, the jury decided the state did not prove that Patrolman Alvin McGill, 27, of 1107 E. Eighth St., Sanford, took $20 from a wallet the Sanford Police Department planted on Feb. 27.

When the verdict was announced, McGill's mother cried, ''Thank you Jesus, Hallelujah.'' The officer put his face in his hand and wiped tears from his eyes.

McGill has been suspended with pay since Feb. 27. Sanford Police Chief Steve Harriett said the officer would be back on the job ''as soon as we work out the details.''

To test McGill's ''integrity,'' police Det. Sgt. Bill Hasson said he put the money in the wallet and instructed a woman acting as a police informant to report to McGill that she found it in a telephone booth outside a Sanford restaurant.

Debbie Mittan testified that she put the wallet on a shelf under the telephone booth outside the Foxfire Restaurant, 3221 U.S. Highway 17-92. McGill said he found no money in the wallet when he arrived a few minutes later.

The case was declared a mistrial on May 31 after jurors could not reach a unanimous verdict. They had been split 5 to 1 in favor of acquittal.

Defense attorney Chris Ray rested his case after telling the jury the police department had not ''covered its bases'' by searching its informant to make sure she did not take the $20. Officers also did not meet McGill at the police station after his shift was over and waited eight hours before confronting him about the money, he said.

''If you're going to try to sting somebody or set him up,'' Ray said. ''You damn well better do a good job of it.''

The prosecution called six witnesses and played a tape recording of Mittan's conversation with McGill to try to prove its case. Hasson said he put the money in the wallet, but Mittan said she never saw it because she never opened it up.